Tris(dialkylamino)sulfonium enolates

Noyori, Ryoji; Nishida, Ikuo; Sakata, J.; Nishizawa, Masatoyo

doi:10.1021/ja00523a082

Cited by 117 publications

(35 citation statements)

References 2 publications

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“…9 The hydrazone and enoxysilane functions of 18 were envisioned to serve as handles for bond formation to the naphthoquinone. We discovered that activation of 18 with tris-(diethylamino)sulfonium difluorotrimethylsilicate [TASF(Et)] 10 in the presence of 5,8-dimethoxy-2,3-dibromonaphthoquinone ( 19 ) 11 cleanly formed the α-quinonylated product 20 in 73% yield as a single detectable anti diastereomer ( 1 H NMR analysis).…”

Section: Introductionmentioning

confidence: 99%

Development of Enantioselective Synthetic Routes to (−)-Kinamycin F and (−)-Lomaiviticin Aglycon

et al. 2012

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The development of enantioselective synthetic routes to (–)-kinamycin F (9) and (–)-lomaiviticin aglycon (6) is described. The diazotetrahydrobenzo[b]fluorene (diazofluorene) functional group of the targets was prepared by fluoride-mediated coupling of a β-trimethylsilylmethyl-α,β-unsaturated ketone (38) with an oxidized naphthoquinone (19), palladium-catalyzed cyclization (39→37), and diazo transfer (37→53). The D-ring precursors 60 and 68 were prepared from m-cresol and 3-ethylphenol, respectively. Coupling of the β-trimethylsilylmethyl-α,β-unsaturated ketone 60 with the juglone derivative 61, cyclization, and diazo transfer, provided the advanced diazofluorene 63, which was elaborated to (–)-kinamycin F (9) in three steps. The diazofluorene 87 was converted to the C2-symmetric lomaiviticin aglycon precursor 91 by enoxysilane formation and oxidative dimerization with manganese tris(hexafluoroacetylacetonate) (94, 26%). The stereochemical outcome is attributed to the steric bias engendered by the mesityl acetal of 87 and contact ion pairing of the intermediates. The coupling product 91 was deprotected (tert-butylhydrogen peroxide, trifluoroacetic acid–dichloromethane) to form the chain isomer of lomaiviticin aglycon 98, which cyclizes to (–)-lomaiviticin aglycon (6, 39–41% overall). The scope of the fluoride-mediated coupling process is delineated (nine products, average yield = 72%, Table 2); a related enoxysilane quinonylation reaction is also described (10 products, average yield = 77%, Table 1). We establish that dimeric diazofluorenes undergo hydrodediazotization 3-fold faster then related monomeric diazofluorenes (Table 6). The simple diazofluorene 103 is a potent inhibitor of ovarian cancer stem cells (IC50 = 500 nM).

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Section: Introductionmentioning

confidence: 99%

Development of Enantioselective Synthetic Routes to (−)-Kinamycin F and (−)-Lomaiviticin Aglycon

et al. 2012

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“…Possible explanations for the ul preference that has been observed in the examples cited (1,(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) will be discussed below.…”

Section: Discussionmentioning

confidence: 99%

Cyclic nitronates from the diastereoselective addition of 1-trimethylsilyloxycyclohexene to nitroolefins. Starting materials for stereoselective Henry reactions and 1,3-dipolar cycloadditions

Brook¹,

Seebàch²

1987

Can. J. Chem.

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Induced by a stoichiometric excess of dichloro(diisopropoxy)-titanium, 1-trimethylsilyloxycyclohexene and (E)-nitroolefins (R—CH=CHNO2, R = C6H5, p-C6H4CH3, p-C6H4OCH3, p-C6H4CN, CH3) combine in CH2Cl2 solution at −90 °C preferentially with relative topicity ul, opposite to the corresponding reaction of enolates or enamines. The primary products are the epimeric bicyclic nitronates 4–6, which can be separated, and which are converted by KF in MeOH to the alkyl or aryl (nitroethyl)-substituted cyclohexanones 1 and 2 (Table 1). Instead of being solvolysed, the cyclic nitronates 4–6 can be used for nitroaldol additions to give the trisubstituted hexahydrobenzopyranols 15–19. Alternatively, 4–6 can be used in 1,3-dipolar cycloadditions with acrylates to furnish the tricyclic compounds 22–31. In either case, products with four asymmetric carbon atoms (not including acetal centres) are produced diastereoselectively. The addition described here is yet another example of an ul combination of trigonal centres induced by Lewis acids, overriding the influence of the configuration of the donor component.

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“…As aldolization is driven by chelation, intramolecular addition to afford a robust transition metal aldolate may bias the enolate-aldolate equilibria toward the latter [117]. The failure of tris(dialkylamino)sulfonium enolates to react with aldehydes is attributed to unfavorable enolate-aldolate equilibria [118]. Indeed, upon exposure to basic hydrogenation conditions, keto-enal substrates provide the Scheme 8.27 Reductive aldol cyclization of keto-enones via catalytic hydrogenation.…”

Section: Hydrogenative Aldol and Mannich Additionsmentioning

confidence: 99%

Hydrogenation for C  C Bond Formation

Bower

Krische

2010

Handbook of Green Chemistry

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The formation of chemical bonds between carbon atoms is of fundamental significance. A major goal in the emerging field of green chemistry involves the design of by-product-free chemical processes, especially CÀC bond-forming processes applicable to renewable feedstocks [1]. This objective is aligned with longstanding economic and aesthetic forces that have shaped the field of chemical synthesis and which have given rise to such concepts as atom-economy [2], step-economy and the ideal synthesis [3]. As revealed by the E-factor (kilogram of waste generated per kilograms of product) [4], it is not surprising that an inverse correlation between process volume and waste generation exists in the chemical industry. For largevolume processes, where minute improvements in efficiency confer significant economic return, by-product-free chemical processes are desirable as they mitigate costs associated with waste disposal and product isolation. Here, fiscal natural selection mandates the practice of green chemistry. In contrast, the fine chemical and pharmaceutical industrial segments often engage in multi-step syntheses where the value of late-stage intermediates can easily exceed the cost of waste stream disposal or product separation, undermining motivation to develop by-product-free protocols (Table 8.1).Must waste production generally increase with increasing molecular complexity? What transformations would be practiced on a vast scale if only efficient by-productfree variants were developed? In the specific case of CÀC bond-forming processes, especially those involving non-stabilized carbanions and their equivalents, a significant cause of waste production resides in the use of stoichiometrically preformed organometallic reagents, which give rise to equimolar quantities of chemical byproducts in the form of metal salts. For example, the vinylation and allylation of carbonyl compounds and imines, which are core reactions in synthetic organic chemistry, uniformly employ preformed vinylmetal and allylmetal reagents. The Green Catalysis, Volume 1: Homogeneous Catalysis. Edited by Robert H. Crabtree

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Tris(dialkylamino)sulfonium enolates

Cited by 117 publications

References 2 publications

Development of Enantioselective Synthetic Routes to (−)-Kinamycin F and (−)-Lomaiviticin Aglycon

Development of Enantioselective Synthetic Routes to (−)-Kinamycin F and (−)-Lomaiviticin Aglycon

Cyclic nitronates from the diastereoselective addition of 1-trimethylsilyloxycyclohexene to nitroolefins. Starting materials for stereoselective Henry reactions and 1,3-dipolar cycloadditions

Hydrogenation for C  C Bond Formation

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